Electrode array having concentric split ring electrodes and methods of making the same

ABSTRACT

A device for brain stimulation includes a lead body having a longitudinal surface and a distal end. The device further includes at least one ring array. The at least one ring array includes a plurality of split ring electrodes disposed on the distal end of the lead body. Each of the plurality of split ring electrodes includes a stimulating portion and a base portion coupled to the stimulating portion. The split ring electrodes of the at least one ring array are arranged about the circumference of the lead body. At least a portion of the base portion of at least one of the plurality of split ring electrodes is disposed below, and insulated from, at least a portion of the stimulating portion of another of the plurality of split electrodes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. §119(e) of U.S.Provisional Patent Application Ser. No. 61/265,243 filed on Nov. 30,2009, which is incorporated herein by reference.

FIELD

The invention is directed to devices and methods for brain stimulationincluding deep brain stimulation. In addition, the invention is directedto devices and method for brain stimulation using a lead havingconcentric split ring electrodes.

BACKGROUND

Deep brain stimulation can be useful for treating a variety ofconditions including, for example, Parkinson's disease, dystonia,essential tremor, chronic pain, Huntington's Disease, levodopa-induceddyskinesias and rigidity, bradykinesia, epilepsy and seizures, eatingdisorders, and mood disorders. Typically, a lead with a stimulatingelectrode at or near a tip of the lead provides the stimulation totarget neurons in the brain. Magnetic resonance imaging (MRI) orcomputerized tomography (CT) scans can provide a starting point fordetermining where the stimulating electrode should be positioned toprovide the desired stimulus to the target neurons.

Upon insertion, current is introduced along the length of the lead tostimulate target neurons in the brain. This stimulation is provided byelectrodes, typically in the form of rings, disposed on the lead. Thecurrent projects from each electrode similarly and in all directions atany given length along the axis of the lead. Because of the shape of theelectrodes, radial selectivity of the current is minimal. This resultsin the unwanted stimulation of neighboring neural tissue, undesired sideeffects and an increased duration of time for the proper therapeuticeffect to be obtained.

In the field of deep brain stimulation, radially segmented electrodearrays (RSEA) have been developed to provide superior radial selectivityof current. Radially segmented electrode arrays are useful for deepbrain stimulation because the target structures in the deep brain areoften not symmetric about the axis of the distal electrode array. Insome cases, a target may be located on one side of a plane runningthrough the axis of the lead. In other cases, a target may be located ata plane that is offset at some angle from the axis of the lead. Thus,radially segmented electrode arrays may be useful for selectivelysimulating tissue. These radially segmented arrays may be made usingconcentric split ring electrodes.

BRIEF SUMMARY

In one embodiment, a device for brain stimulation includes a lead bodyhaving a longitudinal surface and a distal end. The device furtherincludes at least one ring array. The at least one ring array includes aplurality of split ring electrodes disposed on the distal end of thelead body. Each of the plurality of split ring electrodes includes astimulating portion and a base portion coupled to the stimulatingportion. The split ring electrodes of the at least one ring array arearranged about the circumference of the lead body. At least a portion ofthe base portion of at least one of the plurality of split ringelectrodes is disposed below, and insulated from, at least a portion ofthe stimulating portion of another of the plurality of split electrodes.

In another embodiment, a device for brain stimulation includes a leadbody having a longitudinal surface and a distal end. The device furtherincludes a plurality of split ring electrodes disposed on the distal endof the lead body. Each of the plurality of split ring electrodesincludes a stimulating portion and a base portion coupled to thestimulating portion. The split ring electrodes are arranged such thatthe base portions are arranged around an inner circle having a firstradius and the stimulating portions are arranged around an outer circlehaving a second radius, wherein the first radius is less than the secondradius.

In yet another embodiment, a method of manufacturing a device for brainstimulation includes forming a lead body having a longitudinal surfaceand a distal end. At least one ring array is formed. The at least onering array includes a plurality of split ring electrodes at the distalend of the lead body. Each of the plurality of split ring electrodesincludes a stimulating portion and a base portion coupled to thestimulating portion. The split ring electrodes of the at least one ringarray are arranged about the circumference of the lead body. At least aportion of the base portion of at least one of the plurality of splitring electrodes is disposed below and insulated from, at least a portionof the stimulating portion of another of the plurality of splitelectrodes.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting and non-exhaustive embodiments of the present invention aredescribed with reference to the following drawings. In the drawings,like reference numerals refer to like parts throughout the variousfigures unless otherwise specified.

For a better understanding of the present invention, reference will bemade to the following Detailed Description, which is to be read inassociation with the accompanying drawings, wherein:

FIG. 1A is a schematic perspective view of one embodiment of a portionof a lead having a plurality of segmented electrodes and a ringelectrode, according to the invention;

FIG. 1B is a schematic perspective view of another embodiment of a leadhaving a plurality of segmented electrodes arranged in staggeredorientation and a ring electrode, according to the invention;

FIG. 2 is a schematic diagram of radial current steering along variouselectrode levels along the length of a lead, according to the invention;

FIG. 3A is a schematic perspective view of one embodiment of a splitring electrode, according to the invention;

FIG. 3B is a schematic perspective view of another embodiment of a splitring electrode, according to the invention;

FIG. 3C is a schematic cross-sectional view of the split ring electrodeof FIG. 3B, according to the invention;

FIG. 4 is a schematic cross-sectional view of one embodiment of a splitring electrode having an insulative coating, according to the invention;

FIG. 5 is a schematic cross-sectional view of a plurality of split ringelectrodes arranged in a ring array, according to the invention;

FIG. 6 is a schematic perspective view of a plurality of ring arrays anda spacer, according to the invention;

FIG. 7 is a schematic cross-sectional view of one embodiment of aplurality of split ring electrodes having alignment tabs, according tothe invention;

FIG. 8 is a schematic perspective view of a plurality of ring arrayshaving alignment tabs and separated by a spacer, according to theinvention;

FIG. 9A is a schematic perspective view of one embodiment of a portionof a lead having a plurality of split ring electrodes and alignmenttabs, according to the invention;

FIG. 9B is a schematic perspective view of another embodiment of aportion of a lead having a plurality of split ring electrodes andalignment tabs arranged in a staggered orientation, according to theinvention;

FIG. 9C is a schematic perspective view of the portion of the lead ofFIG. 9A after grinding of the alignment tabs, according to theinvention;

FIG. 10 is a schematic side view of one embodiment of a device for brainstimulation, according to the invention.

DETAILED DESCRIPTION

The present invention is directed to the area of devices and methods forbrain stimulation including deep brain stimulation. In addition, theinvention is directed to devices and method for brain stimulation usinga lead having a plurality of split ring electrodes arranged in a ringarray.

A lead for deep brain stimulation may include stimulation electrodes,recording electrodes, or a combination of both. A practitioner maydetermine the position of the target neurons using the recordingelectrode(s) and then position the stimulation electrode(s) accordinglywithout removal of a recording lead and insertion of a stimulation lead.In some embodiments, the same electrodes can be used for both recordingand stimulation. In some embodiments, separate leads can be used; onewith recording electrodes which identify target neurons, and a secondlead with stimulation electrodes that replaces the first after targetneuron identification. A lead may include recording electrodes spacedaround the circumference of the lead to more precisely determine theposition of the target neurons. In at least some embodiments, the leadis rotatable so that the stimulation electrodes can be aligned with thetarget neurons after the neurons have been located using the recordingelectrodes.

Deep brain stimulation devices and leads are described in the art. See,for instance, U.S. Patent Publication 2006/0149335 A1 (“Devices andMethods For Brain Stimulation”), and co-pending patent application U.S.Ser. No. 12/237,888 (“Leads With Non-Circular-Shaped Distal Ends ForBrain Stimulation Systems and Methods of Making and Using”). Each ofthese references is incorporated herein by reference in its respectiveentirety.

FIG. 10 illustrates one embodiment of a device for brain stimulation.The device includes a lead 100, segmented electrodes 1020, a connector1040 for connection of the electrodes to a control unit, and a stylet1050 for assisting in insertion and positioning of the lead in thepatient's brain. The stylet 1050 can be made of a rigid material.Examples of suitable materials include tungsten, stainless steel, orplastic. The stylet 1050 may have a handle 1060 to assist insertion intothe lead, as well as rotation of the stylet 1050 and lead 100.

In one example of operation, access to the desired position in the braincan be accomplished by drilling a hole in the patient's skull or craniumwith a cranial drill (commonly referred to as a burr), and coagulatingand incising the dura mater, or brain covering. The lead 100 can beinserted into the cranium and brain tissue with the assistance of thestylet 1050. The lead can be guided to the target location within thebrain using, for example, a stereotactic frame and a microdrive motorsystem. In some embodiments, the microdrive motor system can be fully orpartially automatic. The microdrive motor system may be configured toperform one or more the following actions (alone or in combination):rotate the lead, insert the lead, or retract the lead. In someembodiments, measurement devices coupled to the muscles or other tissuesstimulated by the target neurons or a unit responsive to the patient orclinician can be coupled to the control unit or microdrive motor system.The measurement device, user, or clinician can indicate a response bythe target muscles or other tissues to the stimulation or recordingelectrode(s) to further identify the target neurons and facilitatepositioning of the stimulation electrode(s). For example, if the targetneurons are directed to a muscle experiencing tremors, a measurementdevice can be used to observe the muscle and indicate changes in tremorfrequency or amplitude in response to stimulation of neurons.Alternatively, the patient or clinician may observe the muscle andprovide feedback.

The lead 100 for deep brain stimulation can include stimulationelectrodes, recording electrodes, or both. In at least some embodiments,the lead is rotatable so that the stimulation electrodes can be alignedwith the target neurons after the neurons have been located using therecording electrodes.

Stimulation electrodes may be disposed on the circumference of the leadto stimulate the target neurons. Stimulation electrodes may bering-shaped so that current projects from each electrode equally inevery direction at any given length along the axis of the lead. Toachieve current steering, segmented electrodes can be utilizedadditionally or alternatively. Though the following descriptiondiscusses stimulation electrodes, it will be understood that allconfigurations of the stimulation electrodes discussed may be utilizedin arranging recording electrodes as well.

FIG. 1A illustrates one embodiment of a lead 100 for brain stimulation.The device includes a lead body 110, one or more ring electrodes 120,and a plurality of segmented electrodes 130. The lead body 110 can beformed of a biocompatible, non-conducting material such as, for example,a polymeric material. Suitable polymeric materials include, but are notlimited to, silicone, polyethylene, polyurethanes, polyureas, orpolyurethane-ureas. In at least some instances, the lead may be incontact with body tissue for extended periods of time. In at least someembodiments, the lead has a cross-sectional diameter of no more than 1.5mm and may be in the range of 0.75 to 1.5 mm. In at least someembodiments, the lead has a length of at least 10 cm and the length ofthe lead may be in the range of 25 to 70 cm.

Stimulation electrodes may be disposed on the lead body 110. Thesestimulation electrodes may be made using a metal, alloy, conductiveoxide, or any other suitable conductive material. Examples of suitablematerials include, but are not limited to, platinum, iridium, platinumiridium alloy, stainless steel, titanium, or tungsten. Preferably, thestimulation electrodes are made of a material that is biocompatible anddoes not substantially corrode under expected operating conditions inthe operating environment for the expected duration of use.

In at least some embodiments, any of the electrodes can be used as ananode or cathode and carry anodic or cathodic current. In someinstances, an electrode might be an anode for a period of time and acathode for a period of time. In other embodiments, the identity of aparticular electrode or electrodes as an anode or cathode might befixed.

The lead contains a plurality of segmented electrodes 130. Any number ofsegmented electrodes 130 may be disposed on the lead body 110. In someembodiments, the segmented electrodes 130 are grouped in sets ofsegmented electrodes, each set disposed around the circumference of thelead at or near a particular longitudinal position. The lead may haveany number of sets of segmented electrodes. In at least someembodiments, the lead has one, two, three, four, five, six, seven, oreight sets of segmented electrodes. In at least some embodiments, eachset of segmented electrodes contains the same number of segmentedelectrodes 130. In some embodiments, each set of segmented electrodescontains three segmented electrodes 130. In at least some otherembodiments, each set of segmented electrodes contains two, four, five,six, seven or eight segmented electrodes. The segmented electrodes 130may vary in size and shape. For example, in FIG. 1B, the segmentedelectrodes 130 are shown as portions of a ring or curved rectangularportions. In some other embodiments, the segmented electrodes 130 arecurved square portions. The shape of the segmented electrodes 130 mayalso be substantially triangular, diamond-shaped, oval, circular orspherical. In some embodiments, the segmented electrodes 130 are all ofthe same size, shape, diameter, width or area or any combinationthereof. In some embodiments, the segmented electrodes of each set (oreven all segmented electrodes) may be identical in size and shape.

In at least some embodiments, each set of segmented electrodes 130 maybe disposed around the circumference of the lead body 110 to form asubstantially or approximately cylindrical shape around the lead body110. The spacing of the segmented electrodes 130 around thecircumference of the lead body 110 may vary. In at least someembodiments, equal spaces, gaps or cutouts are disposed between eachsegmented electrodes 130 around the circumference of the lead body 110.In other embodiments, the spaces, gaps or cutouts between segmentedelectrodes may differ in size or shape. In other embodiments, thespaces, gaps, or cutouts between segmented electrodes may be uniform fora particular set of segmented electrodes or for all sets of segmentedelectrodes. The segmented electrodes 130 may be positioned in irregularor regular intervals around the lead body 110.

Stimulation electrodes in the form of ring electrodes 120 may bedisposed on any part of the lead body 110, usually near a distal end ofthe lead. FIG. 1A illustrates a portion of a lead having one ringelectrode. Any number of ring electrodes may be disposed along thelength of the lead body 110. For example, the lead body may have onering electrode, two ring electrodes, three ring electrodes or four ringelectrodes. In some embodiments, the lead will have five, six, seven oreight ring electrodes. Other embodiments do not include ring electrodes.

In some embodiments, the ring electrodes 120 are substantiallycylindrical and wrap around the entire circumference of the lead body110. In some embodiments, the outer diameter of the ring electrodes 120is substantially equal to the outer diameter of the lead body 110.Furthermore, the width of ring electrodes 120 may vary according to thedesired treatment and the location of the target neurons. In someembodiments the width of the ring electrode 120 is less than or equal tothe diameter of the ring electrode 120. In other embodiments, the widthof the ring electrode 120 is greater than the diameter of the ringelectrode 120.

Conductors (not shown) that attach to or from the ring electrodes 120and segmented electrodes 130 also pass through the lead body 110. Theseconductors may pass through the material of the lead or through a lumendefined by the lead. The conductors are presented at a connector forcoupling of the electrodes to a control unit (not shown). In oneembodiment, the stimulation electrodes correspond to wire conductorsthat extend out of the lead body 110 and are then trimmed or ground downflush with the lead surface. The conductors may be coupled to a controlunit to provide stimulation signals, often in the form of pulses, to thestimulation electrodes.

FIG. 1B is a schematic perspective view of another embodiment of a leadhaving a plurality of segmented electrodes. As seen in FIG. 1B, theplurality of segmented electrodes 130 may be arranged in differentorientations relative to each other. In contrast to FIG. 1A, where thethree sets of segmented electrodes are aligned along the length of thelead body 110, FIG. 1B displays another embodiment in which the threesets of segmented electrodes 130 are staggered. In at least someembodiments, the sets of segmented electrodes are staggered such that nosegmented electrodes are aligned along the length of the lead body 110.In some embodiments, the segmented electrodes may be staggered so thatat least one of the segmented electrodes is aligned with anothersegmented electrode of a different set, and the other segmentedelectrodes are not aligned.

Any number of segmented electrodes 130 may be disposed on the lead body110 in any number of sets. FIGS. 1A and 1B illustrate embodimentsincluding three sets of segmented electrodes. These three sets ofsegmented electrodes 130 may be disposed in different configurations.For example, three sets of segmented electrodes 130 may be disposed onthe distal end of the lead body 110, distal to a ring electrode 120.Alternatively, three sets of segmented electrodes 130 may be disposedproximal to a ring electrode 120. By varying the location of thesegmented electrodes 130, different coverage of the target neurons maybe selected. For example, a specific configuration may be useful if thephysician anticipates that the neural target will be closer to thedistal tip of the lead body 110, while another arrangement may be usefulif the physician anticipates that the neural target will be closer tothe proximal end of the lead body 110. In at least some embodiments, thering electrodes 120 alternate with sets of segmented electrodes 130.

Any combination of ring electrodes 120 and segmented electrodes 130 maybe disposed on the lead. In some embodiments the segmented electrodesare arranged in sets. For example, a lead may include a first ringelectrode 120, two sets of segmented electrodes, each set formed ofthree segmented electrodes 130, and a final ring electrode 120 at theend of the lead. This configuration may simply be referred to as a1-3-3-1 configuration. It may be useful to refer to the electrodes withthis shorthand notation. Other eight electrode configurations include,for example, a 2-2-2-2 configuration, where four sets of segmentedelectrodes are disposed on the lead, and a 4-4 configuration, where twosets of segmented electrodes, each having four segmented electrodes 130are disposed on the lead. In some embodiments, the lead will have 16electrodes. Possible configurations for a 16-electrode lead include, butare not limited to 4-4-4-4, 8-8, 3-3-3-3-3-1 (and all rearrangements ofthis configuration), and 2-2-2-2-2-2-2-2.

FIG. 2 is a schematic diagram to illustrate radial current steeringalong various electrode levels along the length of a lead. Whileconventional lead configurations with ring electrodes are only able tosteer current along the length of the lead (the z-axis), the segmentedelectrode configuration is capable of steering current in the x-axis,y-axis as well as the z-axis. Thus, the centroid of stimulation may besteered in any direction in the three-dimensional space surrounding thelead body 110. In some embodiments, the radial distance, r, and theangle θ around the circumference of the lead body 110 may be dictated bythe percentage of anodic current (recognizing that stimulationpredominantly occurs near the cathode, although strong anodes may causestimulation as well) introduced to each electrode as will be describedin greater detail below. In at least some embodiments, the configurationof anodes and cathodes along the segmented electrodes 130 allows thecentroid of stimulation to be shifted to a variety of differentlocations along the lead body 110.

As can be appreciated from FIG. 2, the centroid of stimulation can beshifted at each level along the length of the lead. The use of multiplesets of segmented electrodes 130 at different levels along the length ofthe lead allows for three-dimensional current steering. In someembodiments, the sets of segmented electrodes 130 are shiftedcollectively (i.e. the centroid of simulation is similar at each levelalong the length of the lead). In at least some other embodiments, eachset of segmented electrodes 130 is controlled independently. Each set ofsegmented electrodes may contain two, three, four, five, six, seven,eight or more segmented electrodes. It will be understood that differentstimulation profiles may be produced by varying the number of segmentedelectrodes at each level. For example, when each set of segmentedelectrodes includes only two segmented electrodes, uniformly distributedgaps (inability to stimulate selectively) may be formed in thestimulation profile. In some embodiments, at least three segmentedelectrodes 130 are utilized to allow for true 360° selectivity.

In addition to 360° selectivity, a lead having segmented electrodes mayprovide several advantages. First, the lead may provide for moredirected stimulation, as well as less “wasted” stimulation (i.e.stimulation of regions other than the target region). By directingstimulation toward the target tissue, side effects may be reduced.Furthermore, because stimulation is directed toward the target site, thebattery in an implantable pulse generator may last for a longer periodof time between recharging.

As previously indicated, the foregoing configurations may also be usedwhile utilizing recording electrodes. In some embodiments, measurementdevices coupled to the muscles or other tissues stimulated by the targetneurons or a unit responsive to the patient or clinician can be coupledto the control unit or microdrive motor system. The measurement device,user, or clinician can indicate a response by the target muscles orother tissues to the stimulation or recording electrodes to furtheridentify the target neurons and facilitate positioning of thestimulation electrodes. For example, if the target neurons are directedto a muscle experiencing tremors, a measurement device can be used toobserve the muscle and indicate changes in tremor frequency or amplitudein response to stimulation of neurons. Alternatively, the patient orclinician may observe the muscle and provide feedback.

Radially segmented electrode arrays may be manufactured in a variety ofways. In at least some embodiments, a plurality of split ring electrodesare used to form an array of radially segmented electrodes. Theplurality of split ring electrodes may be modified to utilize differentnumbers of electrodes, to adjust the radial spacing between electrodesor to vary the longitudinal position between levels of electrodes.

FIG. 3A is a schematic perspective view of one embodiment of a splitring electrode 300. As will be explained further below, the shape andsize of the split ring electrode 300 may be modified. The split ringelectrode 300 of FIG. 3A includes a stimulating portion 310, atransition portion 320 and a base portion 330. The split ring electrode300 may be unitarily formed from a metal, alloy, conductive oxide, orany other suitable conductive material. Alternatively, the split ringelectrode 300 may be formed of distinct segmented that are subsequentlycoupled using welding or other suitable methods.

As seen in FIG. 3A, the stimulating portion 310 of the split ringelectrode 300 may be formed in the shape of a portion of a cylinder. Thesize and shape of the stimulating portion 310 will depend on the numberof the split ring electrodes 300 that will be used and the configurationin which they will be used. In some embodiments, the cross-section ofthe stimulating portion 310 creates a semi-cylindrical portion, thoughit will be understood that the stimulating portion 310 may encompass anypart of a cylinder, such as one-quarter, one-third, or two-thirds of acylinder. In at least some embodiments, the arc length of thestimulating portion 310 encompasses a portion of a circle that issmaller than the reciprocal of the number of split ring electrodes 300that will be used at a given level. For example, if three split ringelectrodes 300 are disposed at a given longitudinal level, then the arclength of the stimulating portion of each split ring electrode may beless than one-third of a circle (i.e. less than 120 degrees). Thus, thesum of the arc lengths of the stimulating portions 310 will not equal360 degrees so that gaps are formed between adjacent stimulatingportions 310. These gaps will separate the stimulating portions 310 fromone another and allow the stimulating electrodes 310 to functionindependently.

The split ring electrode 300 also includes a base portion 330. The baseportion 330 may be formed from the same material as the stimulatingportion 310 (e.g. a metal, alloy, conductive oxide, or other conductivematerial). Alternatively, the base portion 330 may be formed of anon-conductive material that is coupleable to the stimulating portion310 through the use of a transition portion 320 as will be describedbelow or through any other suitable method. As seen in FIG. 3A, the baseportion 330 may be formed in a shape similar to the stimulating portion310. In some embodiments, the base portion 330 has a cross-section inthe shape of a portion of a cylinder. The arc-length of this baseportion 330 may be the same, greater than or less than that of thecorresponding stimulating portion 310. Furthermore, the radius ofcurvature of the stimulating portions 310 may be larger than that of thebase portions 330. As will be appreciated by one of ordinary skill inthe art, the length, width and thickness of the base portion 330 andstimulating portion 310 may also be the same or different as desired.For example, in some embodiments, the base portion 330 is formed thickerthan the stimulating portion 310 for overall reinforcement of thestructure.

A transition portion 320 may be formed between the stimulating portion310 and the base portion 330. In at least some embodiments, thetransition portion 320 is configured to allow the interlocking of theplurality of split ring electrodes 300 as will be described in greaterdetail below with reference to FIG. 5. In some embodiments, thetransition portion 320 is a slightly curved member that serves to jointhe stimulating portion 310 and the base portion 330. FIG. 3B is aschematic perspective view of another embodiment of a split ringelectrode 300. As can be appreciated from FIG. 3B, the transitionportion 320 may instead be formed of a substantially straight memberthat connects the stimulating portion 310 and the base portion 330. Itwill be understood that the angle and length of the transition portion320 may be modified.

FIG. 3C is a schematic cross-sectional view of the split ring electrodeof FIG. 3B. The split ring electrode 300 may be configured in a way suchthat the overall cross-sectional shape of the split ring electrode 300resembles two portions of a cylinder assembled end-to-end at atransition portion 320. In embodiments where the split ring electrode300 is formed from one unitary piece, the shape of the split ringelectrode 300 may be provided by stamping the piece into the appropriateshape, although alternatively other methods of manufacture may be used.Manufacturing the split ring electrodes 300 from a stamped unitary piecemay be useful in reducing both the cost and the possibility of anelectrode breakage or failure. In at least some other embodiments, thetransition portion 320 serves to couple a conductive stimulating portion310 with a nonconductive base portion 330.

An insulative coating may be applied to the split ring electrodes 300 toelectrically insulate them from one another. FIG. 4 is a schematicperspective view of one embodiment of a split ring electrode 300 havingan insulative coating 410. As seen in FIG. 4, in some embodiments, thebase portion 330 is coated with an insulative coating 410. Theinsulative coating 410 may include any suitable insulator such as, forexample, silicone, polyurethane, polyetheretherketone, polysulfone,nylon, polytetrafluoroethylene (e.g., Teflon®), or some other implantgrade non-conductive material. In the case of silicone and certain otherinsulators, the insulative coating 410 may be applied using a dipmolding process or any other suitable method. As previously indicated,applying an insulative coating 410 to the base portion 330 may be usefulin electrically separating one split ring electrode 300 from an adjacentsplit ring electrode 300.

In some embodiments, the insulative coating 410 covers the entirety or asubstantial portion of the base portion 330. Preferably, the insulativecoating 410 is applied to cover a portion of the base portion 330 thatwould otherwise be in contact with a stimulating portion 310 of anadjacent split ring electrode 300. In at least some embodiments, theinsulative coating 410 is applied to both the base portion 330 and thetransition portion 320. Alternatively, the insulative coating 410 may beapplied to only part of the transition portion 320 or to only one sideof the transition portion 320. The bottom of the base portion 330, or apart of the base portion 330 might not be insulated.

A conductor (e.g. a wire) 420 may be attached to any portion of thesplit ring electrode 300. As seen in FIG. 4, a conductor 420 may beattached to the base portion 310 of the split ring electrode 300. Thus,in some embodiments, a piece of the insulative coating 410 may beremoved so that that conductor 420 can properly attach to the baseportion 310 of the split ring electrode 300. Any method of removing afragment of the insulative coating 410 may be used. In some embodiments,an ablation process is used to remove a part of the insulative coating410 so that a conductor 420 may be welded to the base portion 330.Alternatively, the conductor 420 may be coupled to the transitionportion 320 or the stimulating portion 330. If the transition portion320 is coated with an insulative coating 410, portions of the insulativecoating 410 may need to be removed as described herein.

FIG. 5 is a schematic cross-sectional view of a plurality of split ringelectrodes 300 arranged in a ring array. In this illustrated embodiment,three split ring electrodes 300 are assembled into a ring array 500. Asseen in FIG. 5, the split ring electrodes 300 may be positioned suchthat the base portion 330 of one split ring electrode 300 is disposedunderneath or radially inward of the stimulating portion 310 of a splitring electrode 300 that is adjacent to the first in thecounter-clockwise direction. It will be appreciated from thecross-section of the ring array 500 that the result of this arrangementdefine two concentric cylinders. The first cylinder is disposed on theinside of the ring array 500 and includes only the base portions 330 ofthe plurality of split ring electrodes 300. A second concentric cylinderis formed over the first cylinder. The second cylinder is formed of thestimulating portions 310 of the plurality of split ring electrodes 300.In some embodiments, the first cylinder is formed to have a radius equalto or slightly larger than the diameter of the lead body on which itwill be disposed.

In some embodiments, it will be desirable to electrically insulate theplurality of split ring electrodes 300 from each other. As can beappreciated from FIG. 5, the insulative coating 410 serves to insulatethe base portion 330 of each of the split ring electrodes 300 from thestimulating portions 310 of the adjacent split ring electrodes 300.Furthermore, as briefly described above, gaps 510 may be formed betweenthe stimulating portions so that they are electrically insulated fromone another. If an insulative coating 410 is applied to the transitionportions 320, the stimulating portions 310 may be extended so that theyabut one another with the insulative coating 410 providing the desiredinsulation between the two stimulating portions 310. Furthermore, itwill be understood that the overlap between the base portion 330 of onesplit ring electrode 300 and a stimulating portion 310 of an adjacentsplit ring electrode 300 may vary. For example, in some embodiments, thebase portion of 330 of one split ring electrode 300 and the stimulatingportion 310 of an adjacent split ring electrode 300 cover the sameradial angle and fully overlap (i.e. the base portion 330 overlaps about95% of the stimulating portion 310). In other embodiments, the baseportion 330 overlaps up to 99% of the stimulating portion 310. In otherembodiments, the base portion 330 overlaps up to 90% of the stimulatingportion 310. In other embodiments, the base portion 330 overlaps up to80% of the stimulating portion 310. In other embodiments, the baseportion 330 overlaps up to 75% of the stimulating portion 310. In otherembodiments, the base portion 330 overlaps up to 60% of the stimulatingportion 310. In other embodiments, the base portion 330 overlaps up to50% of the stimulating portion 310.

Though FIG. 5 illustrates a ring array 500 having three split ringelectrodes 300, any number of split ring electrodes 300 may be used toform the ring array 500. As few as two split ring electrodes 300 may beused to form a ring array 500. In some embodiments, the ring array 500is formed using two, three, four, five, six, eight, ten, or twelve splitring electrodes 300. The split ring electrodes 300 of any given ringarray 500 may be of the same size and shape or they may have differentsizes and/or shapes. For example, the stimulating portions 310 of thesplit ring electrodes 300 may be of the same length or of differentlengths in a ring array 500.

Furthermore, it will be understood that a lead may include any number ofring arrays 500. Each ring array 500 may be configured the same ordifferently than one or more of the others. For example, a lead mayinclude a ring array 500 having three split ring electrodes 300 at afirst level, a second ring array 500 having three split ring electrodes300 at a second level and a third ring array 500 having two split ringelectrodes 300 at a third level to form a lead having a 3-3-2configuration as described above. Thus, at least one ring array 500 maybe formed to have a different configuration than the others as desired.Additionally, ring electrodes 130 may be disposed between ring arrays500 in positions where segmented electrodes are not necessary. In someembodiments, the stimulating portions 310 of different ring arrays 500are radially aligned. In at least some embodiments, stimulating portions310 of different ring arrays 500 are radially offset.

The interlocking and mutually supporting configuration of the ring array500 allows for sturdy electrode construction. This configuration allowseach split ring electrode 300 to support and secure the adjacentelectrode. By forming leads using ring arrays 500 it may be possible toreduce the possibility of lead failure and breakage. Specifically, leadsmanufactured using ring arrays 500 are less prone to failure because thestimulating portions 310 are secured by the base portions 330. Thus,electrodes are less prone to detachment and disconnection from the leadbody.

FIG. 6 is a schematic perspective view of the plurality of split ringelectrodes 300 and a spacer 710. The split ring electrodes 300 arearranged into two ring arrays 500 as described above. In someembodiments, spacers 610 are placed to control the distance between thering arrays 500 and to electrically insulate one ring array 500 fromanother. The spacer 610 may be in the form of a short cylinder or ringthat separates the two rings arrays 500 as illustrated in FIG. 6. Thespacers 610 may be formed of any suitable non-conductive materialcapable of electrically insulating the stimulating portions 310 of thesplit ring electrodes 300. Additionally, in embodiments having gaps 510,the same material used to form the spacers 610 may be used to form alongitudinal spacer between the individual split ring electrodes 300. Itwill be understood that the size and shape of the spacers may be variedto separate the ring arrays 500 as desired. For example, in someembodiments, the spacers 610 have the same longitudinal width as thering arrays 500. Alternatively, the spacers 610 may be wider or narrowerin the longitudinal direction than the ring arrays 500. The spacers 610may also have the same diameter as the ring arrays 500 in order toproduce an isodiametric lead.

After manufacture of the individual components, the spacers 610 and ringarrays 500 may be coupled to a lead body using any suitable method. Insome embodiments, the plurality of split ring electrodes 300 are coupledto create ring arrays 500, and the ring arrays 500 are then slid onto alead body where they will be permanently secured using welding, or asuitable adhesive. The spacers 610 may also be slid onto the lead bodybetween the ring arrays 500.

Because the split ring electrodes 300 may be manufactured separately, insome embodiments it may be useful to have additional methods of aligningthem. For example, to form the ring array 500 described above, each ofthe split ring electrodes 300 must be disposed in the proper positionand orientation. Proper alignment of the split ring electrodes 300 maybe accomplished using alignment tabs as will be described with referenceto FIG. 7.

FIG. 7 is a schematic cross-sectional view of one embodiment of a ringarray having alignment tabs 710. The alignment tabs 710 may be in theform of projecting flaps, extensions, tips, or handles. As seen in FIG.7, in some embodiments, an alignment tab 710 is coupled to thestimulating portion 310 of each of the split ring electrodes 300.Alternatively, the alignment tabs 710 may be unitarily formed with thestimulating portion 310 in the form of an outwardly bent top portion.The alignment tabs 710 may also be coupled to or formed of a portion ofthe transition portion 320 or even the base portion 330. It will beunderstood that the location and the form of the alignment tab 710 maybe modified so long as the structure is able to orient and manipulatethe split ring electrode 300 into a desired position. Using thealignment tabs 710, it may be possible to maintain the gaps 510 betweenthe split ring electrodes 300.

In some embodiments, the base of the alignment tabs 710 may be connectedto the stimulating portion 310, the transition portion 320 or the baseportion 330 and form a notched portion 720. The notched portion 720 maybe configured in any suitable manner that forms a scored or weakenedjoint or seam between the alignment tab 710 and the split ring electrode300. The use of a notched portion 720 is useful if it is desirable toremove the alignment tabs 710 after proper alignment. In this manner,the alignment tabs 710 may simply be broken off the split ringelectrodes 300 after alignment. Alternatively, the tabs 710 can beground down or cut.

FIG. 8 is a schematic perspective view of the plurality of split ringelectrodes having alignment tabs and separated by a spacer. As seen inFIG. 8, the alignment tabs 710 may be used to position the plurality ofsplit ring electrodes 300 into a ring array 500 having gaps 510.Additionally, the alignment tabs 710 may also be useful in positioningone ring array 500 with respect to a second ring array 500. For example,FIG. 8 illustrates two ring arrays 500 that are radially aligned (i.e.the base portions 330, transition portions 320, stimulating portions 310and alignment tabs 710 of each are radially aligned). One of ordinaryskill in the art may quickly appreciate that the ring arrays 500 areradially aligned by observing the positions of the alignment tabs 710.Additionally, if a staggered orientation is desired, the alignment tabs710 may be used to rotate one of the ring arrays 500 about the lead bodyso that the alignment tabs 710 of one ring array 500 are not in linewith the alignment tabs 710 of a second ring array 500.

FIG. 9A is a schematic perspective view of one embodiment of a portionof a lead having a plurality of split ring electrodes and alignmenttabs. With the alignment tabs 710 radially aligned, a lead similar tothat earlier described in FIG. 1A may be formed. However, if a staggeredconfiguration is preferable, the alignment tabs 710 of one ring array500 may be used to rotate the ring array 500 into the staggeredposition. It will be understood that rotation of the ring array 500 mayalso be accomplished without using the alignment tabs 710. FIG. 9B is aschematic perspective view of one such embodiment of a portion of a leadhaving a plurality of split ring electrodes and alignment tabs arrangedin a staggered orientation.

Thus, the ring arrays 500 and the spacers 610 may be correctlypositioned in the longitudinal direction and properly radially aligned.Furthermore, using a welding technique, or a suitable adhesive, the ringarrays 500 and the spacers 610 may be permanently secured to the leadbody 110. The alignment tabs 710 may then be removed if an isodiametriclead is desired. In some embodiments, the alignment tabs 710 are simplybroken off at the notched portion 720. In at least some otherembodiments, the lead having ring arrays 500 and spacers 610 may beground to the appropriate diameter. FIG. 9C is a schematic perspectiveview of the portion of a lead of FIG. 9A after grinding or otherwiseremoving the alignment tabs 710. In some embodiments, the alignment tabs710 will be removed by grinding the assembled lead, though it will beunderstood that any other suitable method may be used to remove thealignment tabs 710.

Modifications of these methods are possible. For example, though thestimulating portions 310 may need to be formed of a conductive material,other materials may be used in forming the base portions 330 and thetransition portions 320. Furthermore, by varying the size and shape ofthe split ring electrodes 300, it may be possible to produce leadshaving different stimulation and recording advantages. In someembodiments, these methods are used with lead constructions other thandeep brain stimulation leads.

The above specification, examples and data provide a description of themanufacture and use of the composition of the invention. Since manyembodiments of the invention can be made without departing from thespirit and scope of the invention, the invention also resides in theclaims hereinafter appended.

What is claimed as new and desired to be protected by Letters Patent ofthe United States is:
 1. A device for brain stimulation, comprising: alead body having a longitudinal surface and a distal end; at least onering array comprising at least three split ring electrodes disposed onthe distal end of the lead body, each of the at least three split ringelectrodes comprising a stimulating portion and a base portion coupledto the stimulating portion, the stimulating portion extending around aportion of the circumference of the lead body and the base portionextending in a circumferential direction away from the stimulatingportion, the base portion and the stimulating potion each comprising atop surface and a bottom surface opposite the top surface, wherein thesplit ring electrodes of the at least one ring array are arranged aboutthe circumference of the lead body, and wherein at least a portion ofthe base portion of each of the at least three split ring electrodes isdisposed radially below, and insulated from, at least a portion of thestimulating portion of an adjacent one of the at least three splitelectrodes, wherein the top surface of the stimulating portion comprisesat least a section of a circle having a first radius and the top surfaceof the base portion comprises at least a section of a second circlehaving a second radius, the first radius being greater than the secondradius; and an insulative material disposed between the at least threesplit ring electrodes and disposed directly on top of the top surface ofthe base portion of each of the at least three split ring electrodes anddirectly underneath the bottom surface of the stimulating portion ofeach of the at least three split electrodes; wherein the device isconfigured and arranged for brain stimulation.
 2. The device of claim 1,wherein each at least one ring array comprises exactly three spit ringelectrodes.
 3. The device of claim 1, wherein each of the at least onering array comprises at least four split ring electrodes.
 4. The deviceof claim 1, wherein the insulative material comprises an insulativecoating directly on the top surface of the base portion of each of theat least three split ring electrodes.
 5. The device of claim 4, whereinthe insulative coating is applied using a dip-molding process.
 6. Thedevice of claim 1, wherein the at least three split rings electrodes aredisposed on the lead body so that the device is isodiametric.
 7. Thedevice of claim 1, further comprising at least one spacer disposedadjacent to one of the at least one ring array.
 8. The device of claim1, further comprising plurality of conductors coupled to the at leastthree split ring electrodes.
 9. The device of claim 1, wherein thedevice comprises at least two ring arrays, wherein the stimulatingportions of the split ring electrodes of a one of the ring arrays arealigned with the stimulating portions of the split ring electrodes ofanother of the ring arrays.
 10. The device of claim 1, wherein thedevice comprises at least two ring arrays, wherein the stimulatingportions of the split ring electrodes of a one of the ring arrays areoffset from the stimulating portions of the split ring electrodes ofanother of the ring arrays.
 11. The device of claim 1, wherein a portionof the insulative material is disposed directly between the top surface,of the base portion of a one of the split ring electrodes and the bottomsurface of the stimulating portion of another one of the split lingelectrodes.
 12. The device of claim 1, wherein a portion of theinsulative material is disposed radially between the top surface of thebase portion of a one of the split ring electrodes and the bottomsurface of the stimulating portion of another one of the split ringelectrodes.
 13. A device for brain stimulation, comprising: a lead bodyhaving a longitudinal surface and a distal end; at least three splitring electrodes disposed on the distal end of the lead body, each of theat least three split ring electrodes comprising a stimulating portionand a base portion coupled to the stimulating portion, the stimulatingportion extending around a portion of the circumference of the lead bodyand the base portion extending in a circumferential direction away fromthe stimulating portion, the base portion and the stimulating potioneach comprising a top surface and a bottom surface opposite the topsurface; and an insulative material disposed between the at least threesplit ring electrodes and disposed directly on top of the top surface ofthe base portion of each of the at least three split ring electrodes anddirectly underneath the bottom surface of the stimulating portion ofeach of the at least three split electrodes, wherein the split ringelectrodes are arranged such that the top surfaces of the base portionsare arranged around an inner circle having a first radius and the topsurfaces of the stimulating portions are arranged around an outer circlehaving a second radius, wherein the first radius is less than the secondradius, wherein the device is configured and arranged for brainstimulation.
 14. The device of claim 13, wherein the inner circle andthe outer circle are concentric.
 15. The device of claim 13, wherein aportion of the insulative material is disposed directly between the topsurface of the base portion of a one of the split ring electrodes andthe bottom surface of the stimulating portion of another one of thesplit ring electrodes.
 16. An implantable stimulation device,comprising: the device of claim 1; and a control module coupleable tothe lead.
 17. The implantable stimulation device of claim 16, whereinthe implantable stimulation device is a deep brain stimulator.
 18. Amethod of manufacturing a device for brain stimulation, the methodcomprising: forming a lead body having a longitudinal surface and adistal end; and forming at least one ring array comprising at leastthree split ring electrodes at the distal end of the lead body, each ofthe at least three split ring electrodes comprising a stimulatingportion and a base portion coupled to the stimulating portion, thestimulating portion extending around a portion of the circumference ofthe lead body and the base portion in a circumferential direction awayfrom the stimulating portion, the base portion and the stimulatingportion each comprising a top surface and a bottom surface opposite thetop surface, wherein the split ring electrodes of the at least one ringarray are arranged about the circumference of the lead body and whereinat least a portion of the base portion of each of the of at least threesplit ring electrodes is disposed radially below and insulated from, atleast a portion of the stimulating portion of an adjacent one of the atleast three split electrodes by an insulative material disposed betweenthe at least three split ring electrodes and disposed directly on top ofthe top surface of the base portion of each of the at least three splitring electrodes and directly underneath the bottom surface of thestimulating portion of each of the at least three split electrodes,wherein the device is configured and arranged for brain stimulation. 19.The method of claim 18, wherein each of the split ring electrodescomprises at least one alignment tab extending radially outward from thestimulation portion of the split ring electrode, the method furthercomprising aligning the at least one ring array using the alignmenttabs.
 20. The method of claim 19, further comprising grinding thealignment tabs so that the lead body and the at least three split ringelectrodes are isodiametric.